Oxytocin

What it is

Oxytocin is a nine-amino-acid peptide made in the hypothalamus. It is a licensed prescription medicine in the UK (Syntocinon) and elsewhere (Pitocin), used to start or strengthen contractions in labour, to control bleeding after childbirth, and to help with milk let-down. That is what it is approved for.

It is nicknamed the love hormone because it is involved in bonding, trust and social behaviour in animals and people. That has led to nasal sprays and injections being sold for anxiety, social confidence and libido. None of those uses are approved, and the evidence is much weaker than the headlines suggest.

Be wary of anything claiming it makes you trust or bond with someone. Large trials have been disappointing.

History

The effects of pituitary extracts on contractions were observed in 1906 and oxytocin was isolated and synthesised by Vincent du Vigneaud in 1953, earning him the 1955 Nobel Prize in Chemistry. It was the first peptide hormone to be synthesised. Intranasal trials for social behaviour have been run since the 2000s.

How it works

Oxytocin binds receptors on the uterus and mammary glands, and also in brain areas linked to social behaviour and stress. Taken as a nasal spray, a small fraction is thought to reach the brain, although how much is still debated. When injected, it mostly acts in the body, including on the uterus.

Dosage

• There is no approved dose for social, mood or libido use. Clinical trials of the nasal spray have mostly used around 24 IU (roughly 40 mcg) per dose, sometimes once or twice daily.
• Community injection doses are commonly reported at 10-50 mcg subcutaneously, though this is anecdotal. For comparison, 1 IU of oxytocin is about 1.7 mcg.
• Low doses and occasional use are the norm. Higher is not better: some studies suggest bigger doses are less effective or more variable.
• Do not use during pregnancy, as it causes uterine contractions.

How it is taken

• Nasal spray: used in most of the human trials. A metered spray of a dilute solution in each nostril. The nasal route is the only one with controlled-trial data for brain effects.
• Subcutaneous injection into belly fat with a 29-31G insulin syringe is used by some people, mostly for body effects such as libido, though injection is not expected to deliver much to the brain.
• Sublingual or oral forms are sold. Oxytocin is a peptide and is broken down in the gut, so oral absorption is poor.

How to reconstitute

• 2 mg vial: add 2 ml bacteriostatic water to get 1 mg/ml. That is 10 mcg per unit on a 1 ml syringe, so 20 mcg is 2 units and 50 mcg is 5 units.
• 5 mg vial: add 2.5 ml to get 2 mg/ml. That is 20 mcg per unit, so 20 mcg is 1 unit. For small doses, a more dilute mix is easier to measure, e.g. 5 mg in 5 ml for 1 mg/ml.
• 10 mg vial: add 5 ml to get 2 mg/ml (20 mcg per unit), or 10 ml for 1 mg/ml if the vial can hold it.
• For a nasal spray: 2 mg in 5 ml of sterile saline gives 0.4 mg/ml. A 0.1 ml spray is then about 40 mcg (roughly 24 IU). Use a clean nasal spray bottle, and keep it in the fridge.
• Add water slowly down the vial wall. Swirl gently. Do not shake.

How it should arrive

Sealed glass vial with an intact crimped cap and a small white cake or powder.

How it should look once reconstituted

Clear and colourless. Cloudy solution, flakes or residue mean do not use it.

What to expect, and when

• Effects on the uterus are quick (minutes). Nasal effects in studies are measured within 30-60 minutes of a dose.
• Subjective changes in mood or sociability, where reported, are subtle and short-lived.
• If you do not notice anything over a couple of weeks of occasional use, it is probably not doing anything for you.

Side effects

• Headache, nausea, flushing, lightheadedness.
• Nasal irritation or congestion with sprays.
• Drop in blood pressure and faster heart rate at higher doses.
• Water retention. Oxytocin has some antidiuretic effect, and low sodium (hyponatraemia) is a known risk with large doses or when given in a lot of fluid.
• Mood effects: some people report anxiety or feeling off rather than closer to others.

Risks

• Do not use in pregnancy (risk of contractions) unless prescribed by an obstetric team.
• Heart conditions, low blood pressure, or taking blood-pressure-lowering drugs call for medical advice first.
• Oxytocin is not approved for social, anxiety or sexual use. Reviews of nasal oxytocin for autism and social function show mixed results, and a large US trial in autistic children reported no benefit over placebo.
• Some research suggests oxytocin may increase bias toward your own group, or make people more envious or aggressive in some situations, rather than simply friendlier.
• Research-vial products are unlicensed, with unreliable dosing and sterility.

Potential gains

• Labour induction, postnatal bleeding control and breastfeeding support are its established, licensed uses.
• Some small studies suggest short-term effects on social perception, stress and sexual desire, but results are inconsistent and effects are small.
• Nothing here justifies calling it a mood or confidence treatment.

Other useful information

If your goal is anxiety, low mood or sexual function, there are licensed options with better evidence and a GP or sexual health clinic can discuss them. Oxytocin sold online for these reasons is largely an experiment you carry out on yourself.